Diaphragm-type compressors and pumps



' Dec. 17, 1968 FEUH-I-EBOls ETAL 3,416,453

DIAPHRAGM-TYPE COMPRES SORS AND PUMPS Filed March 8, 1967 2 Sheets-Sheet1 [an/s [evil/chads 8ND Germain mat hand/rap; mzgida w L. FEUILLEBOISETAL- 3,416,453 I Dec. 17, 1968 DIAPHRAGM-TYPE COMPRESSOR S AND PUMPS 2Sheets-Sheet 2 Filed March 8. 1967 1011/5 Q //eb0i$ 191/1 fer/"ail!0/7210! United States Patent DIAPHRAGM-TYPE COMPRESSORS AND PUMPS LouisFeuillebois and Germain Ormut, Paris, France, as-

signors to Societe des Compresseurs a Membrane Corblin Filed Mar. 8,1967, Ser. No. 621,558 Claims priority, application France, Mar. 24,1966,

3 Claims. (Cl. 103-44 This invention is concerned with improvements inor relating to diaphragm-type pumps and compressors.

In apparatus of this character a generally metal diaphragm is positivelyoscillated in the biconcave space formed between a perforated plate anda head carrying the suction and delivery valves. The space left betweenthe driving piston and the diaphragm is filled with an intermediateliquid. The apparatus is operated by the piston reciprocationstransmitting a pulsatory motion of same frequency to said diaphragm.

The maximum volumetric efiiciency of the machine is obtained when thediaphragm engages completely the inner surface of the head at eachpiston stroke. As a rule this requirement is met by equipping thecompressor with two ancillary devices as follows:

(1) A hydraulic fluid compensating pump, generally of the sliding pistontype, driven through an eccentric keyed on the main crankshaft of theapparatus, this compensating pump delivering a certain quantity ofhydraulic fluid into the main cylinder at each piston stroke; and

(2) A hydraulic pressure limiting device operating substantially like anoverload valve and adjusted to open at a hydraulic pressuresubstantially higher than the gas pressure obtaining in the circuit fedby the compressor. Thus, the diaphragm contacts the head before thepiston has attained its top dead centre position. Then, as the pistoncontinues its stroke towards the top dead centre it compresses thehydraulic fluid, thus causing the pressure limiting device to open ateach piston stroke.

It is a primary object of this invention to provide, in an apparatus ofthe type set hereinabove, an automatic hydraulic pressure limitingdevice which is both particularly efiicient and constructionally simple.

According to an essential feature of the present invention, thispressure limiting device comprises a valve member adapted to co-act witha seat and responsive on the one hand to the liquid pressure producingthe diaphragm pulsations and on the other hand, through the medium ofspring means, to a differential piston receiving on either faces the gasdelivery pressure.

Besides, it may be noted that in the case of a gas compressor the gaspressure and the hydraulic fluid pressure vary as depicted in thediagrams of FIGURES 1a and 1b, plotting in abscisse the volumesdisplaced by the piston and in ordinates the pressure obtaining in thecompression chamber.

When the compressor or pump delivers fluid at a constant pressure, theoverpressure Ap, to which the diaphragm is subjected at the end of thepiston stroke (FIG- URE la) is constant and in any case consistent withits 'ice mechanical strength. On the other hand, when the compressor orpump operates under variable delivery pressure conditions, notalbly whenfilling a reservoir with compressed \gas, the overpressure Ap applied tothe diaphragm (FIGURE 1b) is subordinate to the gas delivery pressure,for a given setting of the pressure limiting device. Now the lower thegas delivery pressure, the higher this overpressure. Since the pressurelimiting device must be set for a load corresponding to the maximumdelivery pressure attained by the compressor, when this deliverypressure is low a very considerable pressure difference Ap is exertedagainst the diaphragm and is likely to be detrimental to its mechanicalstrength.

It is another object of this invention to avoid this inconvenience byproviding the compressor or pump with an automatic hydraulic pressurelimiting device adapted, irrespective of the conditions of operation ofthe machine, to maintain a constant ratio between the compressordelivery gas pressure and the hydraulic fluid pressure corresponding tothe opening of the pressure limiting device.

In order to afford a clearer understanding of this invention and of themanner in which the same may be carried out in practice, reference willnow be made to the accompanying drawings illustrating diagrammaticallyby way of example a typical form of embodiment of a hydraulic pressurelimiting device according to this invention, which incorporates theimprovements broadly set forth hereinalbove. In the drawings:

FIGURE 2 is a general axial sectional view of a diaphragm-typecompressor incorporating an automatic hydraulic pressure limiting deviceaccording to this invention; and

FIGURE 3 is an axial detail view showing on a larger scale the automatichydraulic pressure limiting device.

As shown in FIGURE 2, the compressor comprises in the known manner ahead 10, a plate 11 and an intermediate perforated plate 12 formed withthrough holes 13, the head 10 and plates 11, 12 being assembled by meansof bolts 14. A suitable gasket 15 is interposed between the intermediateperforated plate 12 and the lower plate 11.

A diaphragm or membrane 16 is clamped along its outer periphery betweenthe head 10 and the intermediate plate 12, thus forming thevariable-volume chamber '17 of the compressor. In the head 10 a deliveryvalve 18 and a suction valve 19 are mounted, as shown.

Coaxially to the lower plate 11 is a cylinder 20 having slidably mountedtherein a piston 21 and leading into a chamber 22 formed between theintermediate plate 12 and the lower plate 11.

Journalled in a member 23 rigid with the lower end of piston 21 andslidalbly mounted in adequate guide means 24 is a gudgeon pin 25connecting the piston 21 to the small end of a connecting rod 26 havingits big end rotatably and drivingly mounted on a crankshaft 27. Thiscrankshaft 27 is rotatably mounted in turn in a crankcase 28 by means ofsuitable bearings 29, 30 and driven by means of a grooved pulley 31. Therotation of this pulley 31, driven from a suitable motor (not shown),causes the reciprocation of piston 21 and the liquid fluid, for instanceoil, contained in the cylinder 20 communicates to the diaphragm 16 apulsatory motion having the same frequency as the piston reciprocations.The volumetric variations resulting from these pulsations in chamber 17cause the fluid to be sucked from an inlet pipe 32 and delivered underpressure into pipe 33.

This apparatus further comprises a hydraulic fluid compensating pump 3-4driven through an eccentric 35 keyed on the main crankshaft 27. Thispump communicates on the one hand with the 'sump 36 of crankcase 28 andon the other hand with chamber 22 underneath the inter- 3 mediate plate12 by means of a pipe line '37 comprising a non-return valve 38.

Finally, the apparatus comprises an automatic hydraulic pressurelimiting device 40 constituting the subject-matter of the presentinvention.

In the form of embodiment illustrated in FIGURE 3 this automatichydraulic pressure limiting device comprises a needle poppet 41co-acting with a gaged seat 42 and controlling the outlet of a duct 43communicating with the diaphragm actuating liquid at a pressure P Thisneedle poppet 41 is movable in a chamber 44 communicating in turnthrough a port 45 with the sump 36 of the crankcase 28 of the compressorproducing the liquid pressure.

Coaxially to the needle poppet 41 is a hydraulic servomotor consistingof a cylinder 46 having slidably mounted therein a differential piston47 controlling said needle poppet 41 through the medium of a coilcompression spring 48. The delivery pressure P of the gas compressed bythe diaphragm 16 is transmitted through pipe line 39 and the branchlines 52 and 53 thereof to the two end faces of the differential piston47, Le. its major face 49 and minor face 50. The piston movements arepermitted by the provision of a vent hole 51 communicating with theexternal atmosphere.

During the operation of the device, the needle poppet 41 is subjected tothe above-defined pressure P and the opposite faces 49 and 50 ofdifferential piston 47 are subjected on the other hand to the gaspressure P The respective net surface areas S and S of the piston faces49 and 50 are so calculated that the valve will open when the value ofpressure P is such that the following equality is obtained:

wherein K is a predetermined factor greater than 1.

As the surface area S of face 49 is greater than the surface area S offace 50, the differential piston is responsive to a resultant forcecounteracting the valve unseating movement. The needle poppet 41 openswhen the force applied thereto, which results from the hydraulic fluidpressure prevailing in cylinder 20, attains the force of oppositedirection which is exerted on the diff rential piston.

The pressure limiting device illustrated in the drawing furthercomprises adjustable end stops 54 and 55 disposed at either end of thehydraulic servo-motor end adapted to be screwed in or out for settingtheir limit positions as desired.

The function of each adjustable end stop 54, 55 is explainedhereinafter:

In the case of end stop 54, if for any reason the compressor or pumpwere subjected to a particularly high delivery pressure likely to impairthe mechanical strength of the machine (for instance in case ofaccidental closing of the delivery valve of the machine), due to theautomatic operation of the pressure limiting device a highly detrimentalhydraulic overpressure may develop in cylinder 20. To avoid thisdrawback, the end stop 54 is so adjusted that when the gas deliverypressure P exceeds a limit value P the differential piston 47 will abutagainst the registering face 56 of this end stop 54. Under theseconditions, the spring 48 is compressed with a force corresponding to apredetermined opening pressure of needle poppet 41. Under theseconditions, the apparatus operates as a relief or safety valve.

In the case of the other end stop 55, if when the compressor is startedno gas pressure is exerted against the differential piston 47 (forexample when it is desired to fill up with gas an initially emptyreservoir), the needle poppet 41 responsive to the pressure prevailingin cylinder 20 as a consequence of the upward stroke of piston 21 willbe unseated and thus cause a hydraulic fluid flow before the diaphragmis urged upwards, so that the compressor will not operate. Thisinconvenience is avoided by the provision of the aforesaid end stop 55.This end stop is so adjusted that before the compressor is started thedifferential piston 47 receives a force urging the needle poppet 41against its seat 42 through the medium of the coil compression spring48.

Of course, this invention should not be construed as being limited bythe specific form of embodiment illustrated and described herein, sincevarious modifications and variations may be brought thereto withoutdeparting from the spirit and scope of the invention as set forth in theappended claims. Thus, notably, the differential piston 47 may compriseon its major face 49 a rod emerging from the outer face of end stop 55.

The applicability of the device is in any way limited to use withdiaphragm-type compressors above described, but may be used withdiaphragm-type compressors embodying somewhat different constructionalfeatures particularly as to method of assembling and sealing of head,method of drive and method of providing oil beneath the diaphragm.

What is claimed is:

1. In a diaphragm-type fluid compressor, comprising a diaphragm, twochambers separated by said diaphragm, a driving piston communicatingwith one of said chambers and the space between said driving piston andsaid diaphragm being filled with a liquid, suction and delivery valvesin the other chamber, an automatic hydraulic pressure limiting devicecomprising a movable valve member, a seat engageable by said valvemember, a pipe line connecting said seat to the compressor chambercontaining the liquid acted upon by the compressor piston for pulsatingthe compressor diaphragm, and a differential piston adapted to move saidvalve member through the medium of a coil compression spring, saiddifferential piston having its minor and major faces both connected tothe gas delivery side of said compressor.

2. In a diaphragm-type fluid compressor, comprising a diaphragm, twochambers separated by said diaphragm, a driving piston communicatingwith one of said chambers and the space between said driving piston andsaid diaphragm being filled with a liquid, suction and delivery valvesin the other chamber, an automatic hydraulic pressure limiting devicecomprising a movable needle poppet, a seat engageable by said needlepoppet and a pipe line connecting said seat to the compressor chambercontaining the liquid acted upon by the compressor piston for pulsatingthe compressor diaphragm, a differential piston adapted to move saidneedle poppet through the medium of a coil compression spring, means forsimultaneously connecting the minor and major faces of said differentialpiston to the gas delivery side of said corn pressor, and adjustable endstop adapted to be engaged by said differential piston when the gasdelivery pressure attains a predetermined value, whereby saiddifferential piston can transmit to said needle poppet a compressiveeffort corresponding to a predetermined valve opening pressure and saidpressure limiting device can operate as a safety valve.

3. In a diaphragm-type fluid compressor, comprising a diaphragm, twochambers separated by said diaphragm, a driving piston communicatingwith one of said chambers and the space between said driving piston andsaid diaphragm being filled with a liquid, suction and delivery valvesin the other chamber, an automatic hydraulic pressure limiting devicecomprising a movable needle poppet, a seat engageable by said needlepoppet and a pipe line connetcing said seat to the compressor chambercontaining the liquid acted upon by the compressor piston for pulsatingthe compressor diaphragm a differential piston adapted to move saidneedle poppet through the medium of a coil compression spring, means forsimultaneously connecting the minor and major faces of said differentialpiston to the gas delivery side of said compressor, a first adjustableend stop adapted to be engaged by one end of said differential pistonwhen the gas delivery pressure attains a predetermined value wherebysaid differential piston can transmit to said needle poppet acompressive effort corresponding to a predetermined value openingpressure and said pressure limiting device can operate as a safetyvalve, a second adjustable end stop adapted to be engaged by the oppo- 56 References Cited UNITED STATES PATENTS 1,651,964 12/ 1927 Nelson230-44 2,753,805 7/ 1956 Boivinet 10344 2,971,465 2/1961 Caillaud 103-44ROBERT M. WALKER, Primary Examiner.

